Gears for driving a drum of a ready-mix concrete truck are used to set the drum of the concrete truck in rotation and retract it during rotation; to facilitate filling of the drum; to empty it during rotation, and to transport the ready-mix concrete in the drum, for example, out of the drum. In addition to providing the torque to the drum required for setting it in rotation, the gear's function is to absorb the weight of the drum and the content thereof. In addition, the gear must compensate for relative motion between the drum and the frame of the vehicle, which motions occur when the drum is loaded and the vehicle travels on uneven terrain, for example. For this purpose, the gear is mounted on a base which is connected to the vehicle frame and is flanged to the drum. The gear must have a compact design since only a small installation space is available between the drum and the driver's cab of the vehicle.
EP 1 186 390 B1 discloses a gear for a drive mechanism of a mixing drum, wherein a hydraulic motor is connected directly to a planet carrier of a planetary gear, on the one hand, and to a stationary housing part, on the other hand. The rotary cylinder of the hydraulic motor drives an inner spider gear of the planetary gear, the outer spider gear of which forms the driven part and is connected to the mixing drum. The mixing drum is mounted in the gear with a bearing, which is disposed on the stationary housing and can be, therefore, configured only with a large diameter which results in high costs.
It is, therefore, the object of the present invention to create a compact gear for driving a mixing drum, which gear is characterized by an inexpensive mount.